Commit fc7751a9 authored by Nick Mathewson's avatar Nick Mathewson 🥔
Browse files

Rewrite state transition logic in entry_guards_note_success() 

asn found while testing that this function can be reached with
GUARD_STATE_COMPLETE circuits; I believe this happens when
cannibalization occurs.

The added complexity of handling one more state made it reasonable
to turn the main logic here into a switch statement.
parent 2e2f3a4d

src/or/entrynodes.c

+23 −17
Original line number Diff line number Diff line
@@ -1927,25 +1927,31 @@ entry_guards_note_guard_success(guard_selection_t *gs, 
  }



  unsigned new_state;

  if (old_state == GUARD_CIRC_STATE_USABLE_ON_COMPLETION) {

  switch (old_state) {

    case GUARD_CIRC_STATE_COMPLETE:

    case GUARD_CIRC_STATE_USABLE_ON_COMPLETION:

      new_state = GUARD_CIRC_STATE_COMPLETE;

  } else {

    tor_assert_nonfatal(

               old_state == GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD);



      break;

    default:

      tor_assert_nonfatal_unreached();

      /* Fall through. */

    case GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD:

      if (guard->is_primary) {

      /* XXXX prop271 -- I don't actually like this logic. It seems to make us

       * a little more susceptible to evil-ISP attacks.  The mitigations I'm

       * thinking of, however, aren't local to this point, so I'll leave it

       * alone. */

        /* XXXX prop271 -- I don't actually like this logic. It seems to make

         * us a little more susceptible to evil-ISP attacks.  The mitigations

         * I'm thinking of, however, aren't local to this point, so I'll leave

         * it alone. */

        /* This guard may have become primary by virtue of being confirmed.

        If so, the circuit for it is now complete.

         * If so, the circuit for it is now complete.

         */

        new_state = GUARD_CIRC_STATE_COMPLETE;

      } else {

        new_state = GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD;

      }

      break;

  }



  if (! guard->is_primary) {

    if (last_time_on_internet + get_internet_likely_down_interval()

        < approx_time()) {

      mark_primary_guards_maybe_reachable(gs);